In the related art, a lot of small-sized machine components such as a gear and a spring are mounted on a mechanical timepiece that is one of small-sized precision instrument.
In the related art, these kinds of machine components are mainly manufactured by machining such as punching. However, in recent years, a method of manufacturing these machine components by using electroforming has been adopted. This is because in the electroforming, machining tolerance is smaller in comparison to the machining, and even in a complicated outer shape, manufacturing can be carried out with accuracy. Accordingly, electroforming is a particularly appropriate method in a case of manufacturing fine and precise machine components.
As a method of manufacturing a small-sized component with high dimensional accuracy, for example, a LIGA technology in which photolithography (Lithographie) and electroplating (Galvanoformung) are combined is disclosed (For example, Non-Patent Document 1).
Here, among small-sized machine components that constitute a mechanical timepiece, a component such as a chronograph coupling lever spring has a spring function (hereinafter, referred to as a “spring component”). In this spring component, excellent fatigue properties and high strength are required for improving excellent connectivity with other components. In addition, since the spring component controls connection with other components by repeating loading and unloading, a property for restoring the original shape during unloading are required. That is, properties capable of reducing a permanent strain amount that remains as deformation after unloading, that is, stress relaxation resistance properties are required for the spring component.